1. Field of the Invention
The present invention is in the field of devices to facilitate mechanical patent drawing. More particularly, this inveniton is in the field of devices to facilitate drafting on sheets of the order of up to about 25 by about 40 centimeters (cm.), with indicia to guide a patent draftsman.
2. Description of the Prior Art
It is known in the art of mechanical drawing to use various aids in order to improve the draftsman's productivity. Included in such aids are my Method and Means for Centerless Circle Construction. U.S. Pat. No. 4,589,210, and Guide for Ellipse Construction, U.S. Pat. No. 4,688,330. This idea permits rapid and accurate drafting of families of concentric circles.
In other methods relating to drafting productivity, draftsmen affix the drafting medium to a base in order to work properly on the drawing. They have pinned drawing sheets to wooden boards and taped them to boards of other compositions for years. The fact of the sheet being fastened to the board, however, means that drawing some kinds of lines can be very awkward or difficult, depending on the kind of drawing and the draftsman's abilities. This circumstance lends itself only to modest drafting efficiency.
Fairly often, the draftsman finds it easier to remove the drawing from the board, make the entries necessary, and then re-affix it to the board. This procedure has obvious drawbacks, including the expenditure of time, and the inescapable possibility of misalignment when the drawing is re-affixed. None of this discussion even touches upon the difficulties of fastening the drawing during the intermediate step, which may present alignment problems of its own, or the damage to the drafting medium from repeated taping or tacking.
The modern use of specialized drafting tables has helped to alleviate the problems disucssed here, but has not completely eliminated them, and such devices are priced far beyond the economic reach of the average draftsman; the cost of a specialized table is so large that such a device is beyond the means even of smaller firms.
Devices are known which employ guidelines, such as, e.g., Ellenberger, U.S. Pat. No. 3,739,478. Other devices are known which use magnetic means to hold portions of drafting apparatus together, such as British Pat. No. 2,073,106A issued to Minnesota Mining and Manufacturing Company. However, none of the devices permit a ready alignment and realignment of the drafting medium in the course of preparing a patent drawing.